1. Field of the Invention
The present invention relates generally to spinal surgery involving the lower lumbar vertebrae. More specifically, the present invention relates to percutaneous lumbosacral fixation and fusion, and devices for performing these operations.
2. Related Art
It has been estimated that 70% of adults have had a significant episode of back pain. Millions of people suffer from the chronic lower back pain. Many of these people resort to surgical intervention to alleviate their pain. Approximately 95% of spinal surgery involves the lower lumbar vertebrae designated as the fourth lumbar vertebra ("L4"), the fifth lumbar vertebra ("L5"), and the first sacral vertebra ("S1").
Persistent low back pain is attributed primarily to degeneration of the disc connecting L5 and S1. There are two possible mechanisms whereby intervertebral disc lesions can instigate and propagate low back pain. The first theory proposes that the intervertebral disc itself trauma or degeneration and becomes the primary source of low back pain. Proponents of this theory advocate removal of the painful disc to relieve the low back pain. Two extensive procedures are available to remove the disc and fuse the adjacent vertebrae together. One method is to replace the disc with bone plugs by going through the spinal canal on either side of the central nerve bundle. This method requires extensive stripping of the paraspinal musculature. More importantly, there are extensive surgical manipulations within the spinal canal itself. Although the initial proponents of this approach report 90% excellent to good results, subsequent studies have been unable to obtain acceptable outcomes and recommend adding internal fixation to improve fusion rates.
The second procedure is the anterior lumbar fusion which avoids the morbidity of posterior muscle stripping by approaching the spine through the abdomen. Surgeons experienced with this technique also report good to excellent patient results in 90% of cases performed. However, when generally used by practicing surgeons, the procedure was found to have a high failure rate of fusion. Attempts to increase the fusion rate by performing a posterior stabilization procedure have been successful, but the second incision increases the morbidity and decreases the advantages of the technique. Thus, the present surgical techniques available to remove and fuse painful lumbar discs are extensive operative procedures with potentially significant complications.
The other proposed mechanism for the intervertebral disc to cause low back pain concerns its affect on associated supportive tissues. The theory states that disc narrowing leads to stress on all of the intervertebral structures. These include the vertebral bodies, ligamentous supports, and facet joints. Surgeries designed to fuse and stabilize the intervertebral segment can be performed through the posterior approach. This is the original surgical procedure which was used to treat low back pain. This approach again entails extensive muscular stripping and bone preparation.
There is, therefore, no single procedure which is universally accepted to surgically manage low back pain patients. Although with sophisticated diagnostic imaging deranged discs can be identified, the surgical procedures are so extensive that clinical outcomes are not consistently satisfactory. Furthermore, patients undergoing presently available fusion surgery experience uncomfortable, prolonged convalescence.
Presently available surgical fixation and fusion techniques involving the lower lumbar vertebrae thus suffer from numerous disadvantages. The present invention has the objective of overcoming such disadvantages.